Question 305187
what is the tenth term of the geometric sequence 1/2, -1, 2, -4?
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{{{a[1]=1/2}}}, {{{a[2]=-1}}}, {{{a[3]=2}}}, {{{a[4]=-4}}}
{{{r=a[2]/a[1]=(-1)/(1/2)=(-1)(2/1)=-2}}}
{{{r=a[3]/a[2]=(2)/(-1)=-2}}}
{{{r=a[4]/a[3]=(-4)/2=-2}}}

{{{a[n]=a[1]r^(n-1)}}}
{{{a[10]=(1/2)(-2)^(10-1)}}}
{{{a[10]=(1/2)(-2)^9}}}
{{{a[10]=(1/2)(-512)}}}
{{{a[10]=-256}}}


1/2, -1, 2, -4, 8, -16, 32, -64,  128,  -256

Edwin</pre>